Such a blood-sampling device equipped with a safety or protective casing made in a plurality of variations is known from U.S. Pat. No. 5,490,841, DE 691 27 906 T2 (U.S. Pat. No. 5,139,489), DE 692 25 609 (U.S. Pat. No. 5,154,285), and U.S. Pat. No. 3,658,061. Such protective casings are also used for cannulas of injection syringes. In order for the user or a third party to not contact the cannula or any blood drops remaining thereon and also to avoid needle sticks, the protective casing is pivoted flush toward the cannula after completion of blood sampling, which is then received in the protective casing. The protective casing has an elongated, opening as the cannula insertion slot. The cannula enters into this slot once the elongated protective casing is pivoted to fit flush with the cannula.
Retaining means are provided in the protective casing itself to prevent the enclosed cannula from coming out of the protective casing on its own. These retaining means are formed as hooks provided in the compartment surrounded by the protective casing walls, and thus inside the protective casing on the base wall, or in the region of the base, thereof. In these blood-sampling devices the protective casing is mounted via a tab and a retaining ring, either in rigid or pivoting manner on the cannula holder.
The known protective casings have the disadvantage that the retaining hooks cannot safely prevent the cannula from coming is out on its own. It is not impossible for the cannula to slide out laterally from the protective casing along with the free hook ends. This is substantially facilitated, such as described in U.S. Pat. No. 5,490,841, by the fact that the insertion slot opens wider when pressure is applied from the slot side onto the lip extending largely across the entire casing length, which are flexible to ease insertion of the cannula, such that the cannula insertion slot is widened and forced apart. The cannula/needle can then exit unintentionally from the protective casing without any problem. This creates therefore the additional problem that sometimes even contaminated fluid may exit. Aside from this a protective casing equipped with additional retaining means or hooks can only be produced at additional expense and additional holes through the casing (compare to above-mentioned DE 691 27 906 and DE 962 25 609). Finally, the practically required threading of the free cannula end into the hooks requires a certain degree of skill, and particular close attention on the part of the user.